| 摘要 |
PURPOSE:To judge the offset condition of air-fuel ratio with high responsive property in the running region having rich intake air amount while judging accurately same also in the running region having small intake air amount by setting the set time on an abnormality detecting means variably such that the smaller the intake air amount is, the longer the set time is. CONSTITUTION:A series of set time tm which are set such that the lower the rotational frequency of an engine and the intake negative pressure are and the smaller the intake air amount is the longer the set time is, are beforehand stored in a controller 19. The set time tm corresponding to the rotational frequency of the engine and the intake negative pressure is read out of the set time data to vary the set time tm such that the smaller the intake air amount is, the longer the set time is. Thus, in the engine running region having large intake air amount, an air-fuel ratio sensor 17 has high temperature as exhaust temperature rises to improve the responsive property of air-fuel-ratio feedback control. When the intake air amount is small, the set time tm becomes long to judge the deviation of the air-fuel ratio sensor 17 accurately without malfunction. |
